Grub won't display windows

I have dual booted windows and manjaro. Grub won’t show windows for some reason. On executing sudo echo GRUB_DISABLE_OS_PROBER=false >> /etc/default/grub command it shows permission denied. Same with nano.

Hello @Ricksy again :wink:

Please check this:

sudo whoami

Are you root?


ye I am in root


sudo nano /etc/default/grub

does not work?

What says:

LANG=C stat /etc/default/grub
 File: /etc/default/grub
  Size: 2081      	Blocks: 8          IO Block: 4096   regular file
Device: 813h/2067d	Inode: 523769      Links: 1
Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2021-08-11 06:06:28.717917164 +0530
Modify: 2021-08-11 16:53:48.773996695 +0530
Change: 2021-08-11 16:53:48.773996695 +0530
 Birth: 2021-08-11 06:04:24.561254760 +0530</pre>
  1. sudo works
  1. Write permissions for root are there…

Normally there should be no problem…

Is the partition mounted read-only?

mount | egrep "/sd[a-z]|/nvme"

I don’t think so
It shows rw

You cannot change a write protected file that way.

If you were to alter a system file that way you would need to do something like this

echo GRUB_DISABLE_OS_PROBER=false | sudo tee -a /etc/default/grub 

But I don’t think your issue lies there - more likely your system has both Legacy boot and EFI boot enabled which will boot Legacy first - then EFI.

When a system is setup this way your Windows system is installed using BIOS/GPT and the Manjaro ISO will EFI boot and the installer will install in EFI mode.

There is very few clues to the user running the installation that the previous system is installed using BIOS mode as the disk is GPT partitioned which is a requirement for EFI.

This leads to an installation where the Grub bootloader in EFI mode doesn’t know of the other system on the disk because it is not EFI.

Most of the linux bootloaders installed for one firmware type cannot launch or chainload bootloaders of the other firmware type. That is, if Arch is installed in UEFI/GPT or UEFI/MBR mode in one disk and Windows is installed in BIOS/MBR mode in another disk, the UEFI bootloader used by Arch cannot chainload the BIOS installed Windows in the other disk. Similarly if Arch is installed in BIOS/MBR or BIOS/GPT mode in one disk and Windows is installed in UEFI/GPT in another disk , the BIOS bootloader used by Arch cannot chainload UEFI installed Windows in the other disk.


and what about another file? Does it effect only the grub file?

So I have to reinstall windows using efi mode for it to work?

I don’t think you need to reinstall anything - I think you can use your firmwares boot-override to select which system to boot.

On Lenovo laptops this is F12 and on a Clevo it is usually F7 - you will have to check you system’s documentation to see which one is applicable.

But in case you decide for it - the systems must be installed in same mode for the grub bootloader to be able to display both.

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